Adhesive composition

ABSTRACT

AN ADHESIVE COMPOSITION AND METHOD OF MAKING SUCH COMPOSITION ARE DISCLOSED. THE COMPOSITION IS SUITABLE FOR USE IN BONDING CARPETING YARNS TO CARPET BACKING. THE COMPOSITION CONSISTS ESSENTIALLY OF HYDROXY MEMEMETHACRYLIC ACID ESTER LATEX, A MELAMINE FORMALDEHYDE CONDINSATE, DODECENYL SUCCINIC ANHYDRIDE AND ZINC OXIDE.

United States Patent Ofifice U.S. Cl. 260-294 UA 15 Claims ABSTRACT OF THE DISCLOSURE An adhesive composition and method of making such composition are disclosed. The composition is suitable for use in bonding carpeting yarns to carpet backing. The composition consists essentially of hydroxy methacrylic acid ester latex, a melamine formaldehyde condensate, dodecenyl succinic anhydride and zinc oxide.

This application is a continuation-in-part of copending application, Ser. No. 864,205, filed Oct. 6, 1969, now US.

Pat. No. 3,645,951.

BACKGROUND OF THE INVENTION In the manufacture of tufted carpeting, yarns of a textile fibrous material, which may be of natural origin such as wool, mohair, cotton, etc., or a synthetic fiber such as a polyamide, viscose rayon, polyesters, polyacrylonitrile or the like, are pushed through a fabric backing such as a non-woven fabric or a woven fabric as, for example, burlap or cotton. An adhesive is applied to the yarn loops which are in contact with the back side or ultimate bottom of the carpet to bond the yarns to the backing. A secondary backing, which may also be a woven or non-woven fabric or foamed latex backing such as shown in US. Pat. 3,215,647,'may then be placed over the loops and primary backing. If the secondary backing is sufficiently open, the adhesive may be applied after the secondary backing is in place. Otherwise, the secondary backingis placed over the wet adhesive which has been,

previously applied to the primarybacking and yarn loops. The yarns which are on the front or ultimate top side of the carpet are frequently cut and are thus bonded in place by the described adhesive. If a secondary backing is also used, the'adhesive likewise, of course, holds such backing in place.

Adhesives previously available for the bonding of carpet yarns to a carpet backing having generally been based on a natural or synthetic latex, as, for example, that disclosed in 'U.'S. Pat. 2,748,446. Such compositions, however, have possessed several limitations. In the first place, the adhesives do not wet and penetrate the backing and yarns to a sufiicient extent to provide a firm and stable bond. Subsequent cleaning, which involves the use of water and/or detergents, causes rapid deterioration of the limited bond, which results in the yarns (including individual plies in a multiple yarn) or individual fibers or filaments thereof being easily pulled from the backing.

This has been found to be a particularly severe situation with yarns of fibrous materials such as mohair, nylon-Q polyesters and acrylics, which do not have scaled sur-" faces or which are not crimped.

-Moreover, piece'dyeing of carpeting made with such adhesives, which involves hot or boiling aqueous dye solutions, causes rapid deterioration of the adhesive bond, also adhesive compositions, even after curing, often contain components which leach out into the dye bath, which has deleterious results such as causing uneven dyeing, particularly with certain synthetic yarns. Also, the adhesives often do not cure well or rapidly at elevated temperatures and coagulate to tacky accumulations which requires one or two additional passes through the curing oven or even standing overnight to complete the cure. Another very serious limitation of such adhesives has been found to be poor shelf life in the container, the adhesive gelling in relatively short periods of time.

This is especially important, since it is quite advanta geous in the manufacture of carpet to utilize containers capable of holding large quantities of the adhesive which can be used over an extended period of time. In addition to the foregoing limitations, adhesive compositions previously available for the specified use have been susceptible to relatively rapid surface hardening upon exposure to the atmosphere and also poor flexibility after curing.

SUMMARY OF THE INVENTION The present invention is thus directed to an adhesive composition and method of making the same, which composition is not susceptible to the foregoing disadvantages. The composition consists essentially of a hydroxy acrylic acid ester latex, a melamine formaldehyde condensate, dodecenyl succinic anhydride and zinc oxide in specified proportions. The hydroxy acrylic acid ester latex is used in a quantity of from about 45 to about parts by weight of acrylic latex solids, while from about 1 to about 2.5 parts by weight of the melamine condensate, 0.5 to about 2 parts by weight of the anhydride and from about 6 to about 15 parts by Weight of zinc oxide, preferably from about 6 to about 12 parts by weight, are used. The composition may also include about 1 part by weight of calcium hydroxide and/or magnesium hydroxide as a filler. The composition has a pH within the range of from about 6 to about 7, with a pH of from about 6.1 to about 6.8 being preferred.

The adhesive composition is preferably prepared as follows. The melamine formaldehyde condensate and the dodecenyl succinic anhydride are first mixed at a temperature of from about to about F. The resulting mixture is then mixed with the hydroxy acrylic acid ester latex at a temperature of from about 100 to about F. To the resulting mixture is then mixed the zinc oxide (dry), and, at about the same time, the calcium and/or magnesium hydroxide, if used, at a temperature of. from about 100 to about F. The final mixture is at from about 100 to about 140 F. to provide complete blending. The composition may then be cooled to The preferred material is a poly hydroxyalkylmethacrylate v in which the alkyl group contains 2 to 3 carbon atoms, namely, poly hydroxyethylmethacrylate and poly hydroxylpropylmethacrylate.

The second important component of the present adhesive is the melamine formaldehyde condensate. The

Patented Mar. 1 2, 1974 detergent and water resistance to the cured adhesive..

In addition, the dodecenyl succinic anhydride'alters the viscosity of the composition causing it better to wet and.

penetrate yarns and backing evenly, without bleeding out of the top side of the backing, and imparts long shelf life to the adhesive. The zinc oxide stabilizes the composition, including its viscosity as a function of the compositions pH and serves as a curing promoter.

The inclusion of calcium hydroxide and/r magnesium hydroxide is particularly advantageous as a filler to control and adjust the pH of the composition and hence its viscosity. Calcium hydroxide is preferred.

The following is a specific example of the adhesive composition of the present invention and its preparation: with 2.5 parts, by weight, of melamine formaldehyde condensate, essentially methylol melamine (in the form of a high viscosity liquid containing 80% solids and providing 2 parts of melamine formaldehyde condensate solids) are mixed 2 parts, by weight, of dodecenyl succinic anhydride, at 120 F. The resulting mixture is then added to and mixed with 180 parts, by weight, of hydroxy acrylic latex (essentially poly hydroxyethylmethacrylate, 50% solids, providing 90 parts, by weight, of solids), at 125 F. There are then added 12 parts, by weight, of zinc oxide (oven dried) and 1 part of calcium hydroxide, and the total is heated, while mixing, at 140 F. The resulting adhesive has a pH of about 6.2. Poly hydroxypropylmethacrylate latex may be used to replace some or all of the poly hydroxyethylmethacrylate.

The adhesive composition of the present invention has an excellent shelf life, having stood in a closed container for 3 months without any apparent change. Moreover, it has been cooled in a refrigerator without the deleterious results often noted with other latex compositions. When applied to yarn loops and adjacent backing, it readily wets them penetrating into the yarns and the backing without, however, bleeding through deleteriously to the front or ultimate top side of the carpeting. On heating to from about 215 to about 300 F. for curing, the adhesive cures completely and evenly in 1-2 minutes depending upon the temperature. Curing the adhesive at elevated temperatures does not result in discoloration thereof (staining) as has been found to be the case with most other latex adhesives. Carpeting made using the present adhesive can be, in the cured or partial- 1y cured conditions, subjected to piece dyeing (the heat encountered during piece dyeing and setting being relied upon to complete the cure, if necessary) without weakening the bond, causing deterioration of the adhesive or loss of fiber into the dye bath. Moreover, the composition is compatible with other aspects of carpet manufacture; for example, nothing leaches from the adhesive into the piece dye bath to contaminate the latter. The cured adhesive is flexible and resilient and is not adversely affected by detergent solutions commonly used in cleaning (shampooing) carpeting. It has also been found to be fire resistant according to AATCC test methods 33-1962 and 34-1966. The cured adhesive has a high degree of porosity and exhibits good aflinity for dyestuffs normally used in piece dyeing carpeting; hence very little or no adhesive can be seen as such after piece dyeing, depending upon the particular dyestuff and yarn. Tufted carpeting made of smooth fibers, utilizing 4 the present adhesive, has been subjected to piece dyeing and to cleaning with detergent soluitons, and the yarns and individual fibers thereof have remained locked in place by the adhesive bond. I

Although further illustrative examples of the adhesive composition, utilizing other quantities of the various components within the specified ranges, could be recited herein, such examples are not necessary for an adequate understanding of the invention. Accordingly, for the sake of brevity of disclosure, no additional examples will be set forth. It should also be understood that one preferred composition contains approximately 90 parts by weight of the described ,acrylic acid ester solids, about 2 parts by weight melamine formaldehyde condensate about 2 parts by weight dodecenyl succinic anhydride,

about- 12 parts by weight zinc oxide, and optionally about 1 part by weight of calcium hydroxide and/ or magnesium hydroxide, with the pH being within the previously indicated preferred range of about 6.1 to about 6.8,

' to provide a composition possessing highly satisfactory- "by Weight zinc oxide.

2. The composition of claim 1 in which said composition has a pH of from about 6 to about 7.

3. The composition of claim 2 in which said composition has a pH of about 6.1 to about 6.8.

4. The composition of claim 1 including about 1 part by weight of calcium hydroxide and/or magnesium hydroxide.

5. The composition of claim 1 wherein said poly hydroxyalkylmethacrylic acid ester latex contains 2 to 3 carbon atoms in the alkyl group.

6. The composition of claim 1 in which said melamine formaldehyde condensate is methylol melamine.

7. The composition of claim 5 in which said melamine formaldehyde condensate is methylol melamine.

8. The composition of claim 7 including about 1 part by weight of calcium hydroxide and/or magnesium hy droxide.

9. An adhesive composition for use in bonding carpeting yarns to carpet backing consisting essentially of from about 45 to about 90 parts by weight of polyhydroxy alkyl methacrylic acid ester latex solids, about 1 to about 2.5 parts by weight of a melamine formaldehyde condensate, about 0.5 to about 2 parts by weight of dodecenyl succinic anhydride, and from about 6 to about 15 parts by weight of zinc oxide, said composition having a pH of from about 6 to about 7, said latex being a poly hydroxyalkylmethacrylate in which-the alkyl group contains 2 to 3 carbon atoms and said melamine formaldehyde condensate is methylol melamine.

. to about 120 F., admixing the resulting mixture with 10. The composition of claim 9 in which said composition has a pH from about 6.1 to about 6.8.

11. The composition of claim 10 in which said zinc oxide is present in a quantity of from about 6 to about 12 parts by weight. v

12. The composition of claim 11 including about 1 part by weight of calcium hydroxide and/or magnesium from about 45 to about parts by weight of polyhydroxy alkyl methacrylic acid ester latex solids at a tem- 5 i 6 perature of from about 100 to about 130' F., and sub- References Cited sequently mix1ug about 6 to about 15 parts by weight UNITED STATES PATENTS of zmc oxide with the resulting mixture at a temperature 0 of from about 100 to about 140 F. 3,645,951 2/1972 Kuias 260-494 U A 14. The method of claim 13 in which about 1 part by weight of calcium hydroxide and/or magnesium hy- 5 LORENZO HAYES 'Pnmary Exammer droxide is mixed with said mixture at about the same U S Cl XR time said zinc oxide is admixed therewith.

15. The composition of claim 1 in which said zinc 260-39 R, 41 B, 856 oxide is present in a quantity of from about 6 to about 10 12 parts by weight. 

